evict larger entries first

net/disk_cache/simple/simple_experiment.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/disk_cache/simple/simple_experiment.h"
 
 #include <map>
 #include <string>
 
 #include "base/metrics/field_trial.h"
 #include "base/metrics/field_trial_param_associator.h"
 #include "base/strings/string_number_conversions.h"
 
 namespace disk_cache {
 
 const base::Feature kSimpleSizeExperiment = {"SimpleSizeExperiment",

[pasko, 2017/06/23 15:10:30]

maybe allow a param like log/sqrt/whatever that you initially considered? Given
that we are running an experiment anyway, it would be a cheap way to discover
whether typical uses are matching the data you experimented with locally.

I'm OK with doing it in a later change.

[hubbe, 2017/06/23 18:25:52]

log & sqrt are too slow, don't make mathematical sense and they don't performed
well in my experiments so far. I'm not going to try that unless there is some
reason suggesting that it would be better.

                                              base::FEATURE_DISABLED_BY_DEFAULT};
+const base::Feature kSimpleCacheEvictionWithSize = {
+    "SimpleCacheEvictionWithSize", base::FEATURE_DISABLED_BY_DEFAULT};

[pasko, 2017/06/23 15:10:30]

does finch config allow enabling more than one feature and providing params for
each one of them?

I think in order for this to allow dropping caches in a no-op group, we would
either need to enable SimpleSizeExperiment or use the similar logic as
CheckForSimpleSizeExperiment/SimpleExperimentMatches.

[hubbe, 2017/06/23 18:25:52]

I don't intend to drop caches in the finch experiment.
If I did, I would use the SimpleExperiment logic in this file to do that.

[pasko, 2017/06/26 13:32:13]

Thank you. I have a few reservations about it, so I started a discussion in the
document.

not lgtm until we reach agreement in the discussion, feel free to throw a VC to
figure out what works for us.

+
 const char kSizeMultiplierParam[] = "SizeMultiplier";
 
 namespace {
 
 // Returns true if the experiment is found and properly defined.
 bool CheckForSimpleSizeExperiment(disk_cache::SimpleExperiment* experiment) {
   DCHECK_EQ(disk_cache::SimpleExperimentType::NONE, experiment->type);
   DCHECK_EQ(0u, experiment->param);
 
   if (!base::FeatureList::IsEnabled(kSimpleSizeExperiment))
@@ skipping 27 matching lines @@
   SimpleExperiment experiment;
 
   if (cache_type != net::DISK_CACHE)
     return experiment;
 
   CheckForSimpleSizeExperiment(&experiment);
   return experiment;
 }
 
 }  // namespace disk_cache